IRS audits you by conducting a paper trail of what YOU do in the us. If you win a world series, earn $20m/film, president of a compny earning $100M in profits last year, $20M endorsement contract (ready to bend over for the IRS Phelps?) blah blah. You can never hide your money.
Like you said, offshore company, you work for them, they bill for your services, they make the money, offshore company held by x,y,z family members - accounts all around the world. Most of those accounts get transferred to worldwide properites, stocks and funds. IRS can't figure out dick. Go look at how Bin Laden hides his money!
Swiss Bank Accounts - hahahaha!
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